Select Columns: Accept partially correct drops

Author: janezd

Orange/widgets/data/owselectcolumns.py

@@ -7,6 +7,7 @@
     Qt, QTimer, QSortFilterProxyModel, QItemSelection, QItemSelectionModel,
     QMimeData, QAbstractItemModel
 )
+from AnyQt.QtGui import QDrag
 
 from Orange.data import Domain, Variable
 from Orange.widgets import gui, widget
@@ -50,6 +51,10 @@ class VariablesListItemModel(VariableListModel):
     """
     MIME_TYPE = "application/x-Orange-VariableListModelData"
 
+    def __init__(self, *args, primitive=False, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.primitive = primitive
+
     def flags(self, index):
         flags = super().flags(index)
         if index.isValid():
@@ -97,7 +102,76 @@ def dropMimeData(self, mime, action, row, column, parent):
         if row < 0:
             row = self.rowCount()
 
+        if self.primitive and not all(var.is_primitive() for var in variables):
+            variables = [var for var in variables if var.is_primitive()]
+            self[row:row] = variables
+            mime.setProperty("_moved", variables)
+            return False
+
         self[row:row] = variables
+        mime.setProperty("_moved", True)
+        return True
+
+
+class SelectListItemView(VariablesListItemView):
+    """
+    VariableListItemView that accepts information on what has been dropped
+
+    At the end of the drag action, only dropped items (i.e. accepted by the
+    target) are removed.
+    """
+    def startDrag(self, supported_actions):
+        indexes = self.selectedIndexes()
+        if len(indexes) == 0:
+            return
+        data = self.model().mimeData(indexes)
+        if not data:
+            return
+        drag = QDrag(self)
+        drag.setMimeData(data)
+        drag.exec(supported_actions, self.defaultDropAction())
+
+        moved = data.property("_moved")
+        if moved is None:
+            return
+
+        if moved is True:
+            # A quicker path if everyhing is moved
+            for index in self.selectionModel().selection():
+                self.model().removeRows(index.top(),
+                                        index.bottom() - index.top() + 1)
+        else:
+            moved = set(moved)
+            for row in sorted((ind.row()
+                               for ind in self.selectionModel().selectedIndexes()
+                               if ind.data(gui.TableVariable) in moved),
+                              reverse=True):
+                self.model().removeRows(row, 1)
+
+
+class FeatureListItemView(SelectListItemView):
+    """
+    A SelectListItemView whose acceptsDropEvent checks if there are any
+    primitive variables. Derived from a class that would reject the drop
+    if there are any non-primitive.
+    """
+    def acceptsDropEvent(self, event):
+        """Should the drop event be accepted?"""
+        # Overridden to allow drops if some, not necessarily all variable types match
+        # disallow drag/drops between windows
+        if event.source() is not None and \
+                event.source().window() is not self.window():
+            return False
+
+        mime = event.mimeData()
+        vars = mime.property('_items')
+        if vars is None:
+            return False
+
+        if not any(var.is_primitive for var in vars):
+            return False
+
+        event.accept()
         return True
 
 
@@ -217,7 +291,9 @@ def update_on_change(view):
 
         self.available_attrs = VariablesListItemModel()
         filter_edit, self.available_attrs_view = variables_filter(
-            parent=self, model=self.available_attrs)
+            parent=self, model=self.available_attrs,
+            view_type=SelectListItemView
+        )
         box.layout().addWidget(filter_edit)
         self.view_boxes.append((name, box, self.available_attrs_view))
         filter_edit.textChanged.connect(self.__var_counts_update_timer.start)
@@ -236,11 +312,12 @@ def dropcompleted(action):
         # 3rd column
         name = "Features"
         box = gui.vBox(self.controlArea, name, addToLayout=False)
-        self.used_attrs = VariablesListItemModel()
+        self.used_attrs = VariablesListItemModel(primitive=True)
         filter_edit, self.used_attrs_view = variables_filter(
             parent=self, model=self.used_attrs,
             accepted_type=(Orange.data.DiscreteVariable,
-                           Orange.data.ContinuousVariable))
+                           Orange.data.ContinuousVariable),
+            view_type=FeatureListItemView)
         self.used_attrs.rowsInserted.connect(self.__used_attrs_changed)
         self.used_attrs.rowsRemoved.connect(self.__used_attrs_changed)
         self.used_attrs_view.selectionModel().selectionChanged.connect(
@@ -263,9 +340,9 @@ def dropcompleted(action):
         name = "Target"
         box = gui.vBox(self.controlArea, name, addToLayout=False)
         self.class_attrs = VariablesListItemModel()
-        self.class_attrs_view = VariablesListItemView(
+        self.class_attrs_view = SelectListItemView(
             acceptedType=(Orange.data.DiscreteVariable,
-                          Orange.data.ContinuousVariable)
+                          Orange.data.ContinuousVariable),
         )
         self.class_attrs_view.setModel(self.class_attrs)
         self.class_attrs_view.selectionModel().selectionChanged.connect(
@@ -279,8 +356,9 @@ def dropcompleted(action):
         name = "Metas"
         box = gui.vBox(self.controlArea, name, addToLayout=False)
         self.meta_attrs = VariablesListItemModel()
-        self.meta_attrs_view = VariablesListItemView(
-            acceptedType=Orange.data.Variable)
+        self.meta_attrs_view = SelectListItemView(
+            acceptedType=Orange.data.Variable,
+        )
         self.meta_attrs_view.setModel(self.meta_attrs)
         self.meta_attrs_view.selectionModel().selectionChanged.connect(
             partial(update_on_change, self.meta_attrs_view))